Re: more on delete from join

From: Joe Thurbon <>
Date: Tue, 01 Sep 2009 08:17:54 GMT
Message-ID: <op.uzkjz4c0q7k8pw_at_imac.local>

On Tue, 01 Sep 2009 14:33:07 +1000, Mr. Scott <> wrote:

> "Marshall" <> wrote in message
> On Aug 30, 11:52 pm, "Mr. Scott" <> wrote:
> <snip>
> <quote>
>> > Some systems of equations are overspecified, some are underspecified,
>> > and some are uniquely specified. Which one of those do you think
>> > might be a good candidate for the kind of view update that
>> > would succeed? Would fail?
>> I don't think systems of equations apply to view updates, because view
>> updates involve more than one state of affairs, the state before the
>> update
>> and the state after. Systems of equations are either independent of
>> state
>> or involve one and only one state, so I don't think they are even
>> relevant
>> to the problem of view updates.
> To me, the question is, do my ad hoc view update rules give
> better results, or does my equation solving approach work
> better? My expectation is that the latter is true, but as I said,
> I haven't worked out all the detail yet.
> </quote>
> While I am still uncomfortable with the idea of the premises of an
> argument
> following from its conclusion,

This pattern of inference is quite well studied. It is called Abductive Inference. It is the oft overlooked cousin of deductive and inductive inference.

Doctors are very fond of it.

Deduction: Given a and a->b infer b
Induction: Given a and b, infer a -> b,
Abduction: Given b and a->b, infer a

It is often known by the highly technical term 'guessing'.

Joe Received on Tue Sep 01 2009 - 10:17:54 CEST

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